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Functional CB2-receptors can also be found in the brain. This is the striking conclusion of the paper Excitability of prefrontal cortical pyramidal neurons is modulated by activation of intracellular type-2 cannabinoid receptors, published in the February 2012 issue of Proceedings of the National Academy of Sciences and written by, amongst others, Femke den Boon, Pascal Chameau, Wytse Wadman en Taco Werkman (SILS).

CB-receptors are part of the endocannabinoid system and are sensitive to cannabis-like chemicals produced by the body. There are two types of CB-receptors: CB1- and CB2-receptors. ‘The location of CB1-receptors in neurons -namely on the cell membrane- and in certain areas of the brain is well-documented’, according to researcher den Boon. The location of the CB2-receptors, however, was still unclear. The receptors were previously found in more peripheral tissues, such as in the immune system, and were therefore not expected in the brain.

Now, den Boon et al. have shown otherwise. Using a combination of biochemical and electrophysiological techniques, the researchers demonstrated the presence of CB2-receptors in the prefrontal cortex (an area of the brain involved in higher cognitive functions, such as decision-making and working memory) of mice and rats. Likely, CB2-receptors can also be found in other parts of the brain, as well as in human brains.

Remarkably, the CB2-receptors are located not on the cell membrane as CB1-receptors, but inside the cell. Possibly, this increases the length of time before signals reach the receptors, providing some unknown advantage to cell functioning. Furthermore, upon activation, CB2-receptors desensitize the surrounding neurons, rendering them less sensitive to other signals. Den Boon is excited about these findings, since they may well form a new method of signal transduction in the brain. She will next concentrate her efforts on determining in what way this new pathway might affect our functioning.

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